The present invention relates to a printed circuit board applicable to various kinds of electronic equipment and, more particularly, to a printed circuit board which allows the characteristic impedance and wavelength reduction ratio of microstrip lines thereof to be measured with ease.
It is a common practice with a printed circuit board to form a strip conductor on one surface of a dielectric substrate and a ground conductor on the other surface, thereby providing a microstrip line with a particular characteristic impedance and a particular wavelength compaction ratio. To measure the characteristic impedance and wavelength compaction ratio of microstrip lines included in a wiring pattern, a desired one of the microstrip lines is electrically disconnected from the surrounding circuitry, and then the characteristic impedance and phase rotation angle are measured by a network analyzer or similar implement. The problem with such a conventional procedure is that neither the characteristic impedance nor the wavelength compaction ratio can be seen unless the microstrip line is disconnected from the surrounding circuit pattern. Specifically, changes in the characteristic impedance and wavelength compaction ratio cannot be readily observed in the event of the revision or modification of printed circuit boards, the change of production lot, the manufacturer's changes, etc. Moreover, the conventional procedure is difficult to practice with a multi-layer printed circuit board having a strip conductor on the inner layer thereof.